Various photosensitive polyimide materials have been proposed. Exemplary such materials include those using a polyamic acid as the precursor of the polyimide such as those of JP-A 49-115541 and JP-A 55-45746 using a polyamic acid having a photosensitive group introduced in the carboxyl group by ester bond, and the material of JP-A 54-145794 comprising a polyamic acid and an amine compound having a photosensitive group. For the formation of the desired polyimide film, these proposals, however, required imidation treatment at a high temperature in excess of 300° C. after the formation of the patterned film, and this led to the problem of limitation of the material that could be used for the substrate since the substrate had to endure the high temperature as well as the problem of the oxidation of the copper used for the interconnection.
One solution to these problems is found in JP-A 10-274850, JP-A 10-265571, and JP-A 2001-335619, which describe photosensitive polyimide materials comprising solvent-soluble resins which have been imidized for the purpose of lowering the curing temperature. Since the resins in these patent documents are rendered photosensitive by incorporating (meth)acrylic radicals, they are susceptible to oxygen interference due to their photo-curing mechanism and also susceptible to film slimming during the development. Accordingly, improvement of the resolution was difficult, and these materials were far from meeting all required properties.
Also proposed are positive compositions comprising a polyimide structure having phenolic hydroxyl radicals (JP-A 3-209478) or a polyamide structure (JP-B 1-46862 and JP-A 11-65107) combined with diazonaphthoquinone. These compositions suffer from the drawbacks that formation of a thick films in excess of 20 μm is difficult due to their light transmittance and that the inherent curability of the resin is not fully utilized because of the reduced molecular weight of the resin for ensuring effective development and increased amount of the diazonaphthoquinone (sensitizer) relative to the resin.